The present invention relates generally to compounds and methods for use in stimulating xcex2-catenin mediated gene expression and cellular differentiation. The invention is more specifically related to modulating agents capable of increasing the level of free xcex2-catenin in a cell cytoplasm, and to therapeutic methods employing such agents.
xcex2-catenin is a cytoplasmic protein that is critical for classical cadherin-mediated intercellular adhesion. Inside the cell, a xcex2-catenin/(xcex1-catenin complex interacts with the second cytoplasmic domain (CP2) of the classical cadherins. In the absence of this xcex2-catenin/xcex1-catenin complex, the classical cadherins cannot promote cell adhesion (see Wheelock et al., Current Topics in Membranes 43:169-185, 1996).
In addition to its role in cell adhesion, xcex2-catenin also appears to be a key component of certain cellular signaling pathways, leading to activation of gene expression and a variety of developmental processes, such as differentiation. In particular, xcex2-catenin functions in Wnt-mediated signaling, associating with LEF-1/TCF DNA binding proteins to form a transcription factor (see FIG. 2). The level of signal transduction appears to correlate with the level of free xcex2-catenin in the cytoplasm of the cell (see Willert and Nusse, Genetics and Development 8:95-102, 1998). Glycogen synthase kinase 3xcex2(GSK-3xcex2) and adenomatous polyposis coli tumor suppressor protein (APC) interact with cytoplasmic xcex2-catenin and facilitate its degradation via the ubiquitin/proteosome pathway (see FIG. 2).
Wnt-mediated signaling is involved in a variety of developmental processes, including cellular differentiation. For example, skin cells expressing a stabilized form of xcex2-catenin display increased hair growth (Gat et al., Cell 95:605-614, 1998; Ono et al., Cell 95:575-578, 1998). Thus, therapies based on increasing the level of free xcex2-catenin in the cytoplasm have potential for stimulating Wnt-mediated signal transduction, resulting in differentiation and, in certain instances, enhanced hair growth. However, there are presently no available therapies for modulating Wnt-mediated signaling.
Accordingly, there is a need in the art for improved methods for inducing Wnt-mediated signal transduction and cellular differentiation. The present invention fulfills this need and further provides other related advantages.
The present invention provides methods for stimulating xcex2-catenin mediated gene transcription and cellular differentiation. Within certain aspects, the present invention provides modulating agents capable of increasing the level of free xcex2-catenin in a cell. In one such aspect, the modulating agent comprises an internalization moiety and one or more of: (a) the amino acid sequence SYLDS(PO4)GIHS(PO4)G (SEQ ID NO:1) or (b) a peptide analogue or peptidomimetic of the amino acid sequence SYLDS(PO4)GIHS(PO4)G (SEQ ID NO: 1). The internalization moiety may comprise, within certain embodiments, an internalization sequence covalently linked to the modulating agent, a liposome that encapsulates the modulating agent or an antibody or ligand that binds to a cell surface receptor. Within further embodiments, any of the above modulating agents may be linked to a targeting agent and/or a drug.
Within other aspects, the present invention provides pharmaceutical compositions comprising a modulating agent as described above, in combination with a pharmaceutically acceptable carrier.
The present invention further provides, within other aspects, methods for increasing the level of xcex2-catenin in a cell, comprising contacting a cell with a modulating agent as described above.
Within further related aspects, the present invention provides methods for stimulating the activation of xcex2-catenin mediated gene transcription in a cell, comprising contacting a cell with a modulating agent as described above.
Within further related aspects, the present invention provides methods for stimulating differentiation of a cell, comprising contacting a cell with a modulating agent as described above. In certain embodiments, the cell is a skin cell, such as a keratinocyte.
In other aspects, methods are provided for stimulating hair growth or reducing hair loss on a mammal, comprising administering to a mammal a modulating agent as described above. Such administration may be topical, and the skin cells may be present, for example, on the scalp or within the ear of the mammal.
The present invention further provides, within other aspects, methods for stimulating exfoliation of skin on a mammal, comprising administering to a mammal a modulating agent as described above.